Submerged structures, for example, ships, port facilities, buoys, pipe lines, bridges, excavators for seabed oil fields, water pipes in electric power plants or seaside plants, fish nets or fish breeding rafts suffer from the adhesion of large-sized animals and plants such as barnacle, hard-shelled mussel and laver and small-sized ones such as diatom and bacteria, which causes various damages, for example, corrosion of the structures, an increase in sea water friction of ships, death of a number of fishes due to fishing net jamming, settling out due to gain in weight and a decrease in operating efficiency. Further, in industrial water systems with the use of natural water such as river water and lake water as, for example, cooling water or in circulating cooling systems with the use of moderately or highly purified city water, the abnormal propagation of, for example, bacteria, diatom, blue-green algae and spirogyra causes various troubles including deterioration of water qualities, a decrease in cooling efficiency and pipe jamming due to the adhesion thereof to the walls of instruments and reduction in flow rate.
In order to prevent these troubles caused by aquatic pests, there have been employed antifouling agents containing inorganic heavy metal compounds such as copper suboxide, copper rhodanide and mercury oxide or organic metal compounds such as tributyltin oxide, triphenyltin oxide and tributyltin (meth)acrylate polymers.
However, these compounds which have been conventionally employed for the above-mentioned purpose are not only highly toxic ones and thus should be handled with religious care but also result in some problems including deformation of fishes due to the accumulation thereof in fish bodies and environmental pollution. Therefore it has been urgently required to use an antifouling agent free from any heavy metals or organic metals.
As such an antifouling agent free from any heavy metals or organic metals, Japanese Patent Laid-Open No. 128302/1991 has proposed the use of alkylphenols. However, these alkyl-phenols are not usable in practice at present, since the effects thereof are lost within only a short period of time.
Accordingly, it is an object of the present invention to provide an antifouling agent scarcely causing any problems in hygienic safety and the environment (namely, having a low toxicity and a low persistence) and being capable of exerting its effects over a long period of time without adversely affecting the ecosystem or the working environment.